c. both a and b
Work Step by Step
The waxy cuticle layer effectively prevents water loss and gas exchange when the stomata are closed. Epidermal cells secrete a substance that contains waxes, pectin, and cellulose fibers sitting within a polymer called cutin; this substance forms a barrier to prevent water from leaving the plant. Additionally, the cuticle prevents the exchange of oxygen and carbon dioxide in the plant, provided the stomata are closed.